In isolation, a 6-0 defeat to Chelsea could be dismissed as a freakish derby day demolition. But the Gunners have a habit of collapsing away from home against fellow title contenders. They went down 6-3 at Manchester City and 5-1 at Liverpool.

They have lost 17-4 on the road against fellow top-four teams.

Arsenal’s hopes of raising the Premier League trophy in May expired before they were reduced to 10 by Andre Marriner sending the wrong man off.

By then they were already 2-0 down after twice losing the ball in the centre of the pitch and failing to react to Chelsea’s counter-attacks.

Even in the warm-up Arsenal looked dopey. In the nostalgic preamble Wenger remembered banning Mars bars before his first game in charge, way back in 1996.

Get them back on the menu.

In those first seven minutes, when Samuel Eto’o and André Schürrle scored, Lukas Podolski was malingering high up the pitch as Chelsea attacked his flank and Arsenal’s defenders retreated as a rabble rather than a defensive unit who had studied Chelsea’s speed on the counter.

The FA Cup still offers salvation for Wenger, who won seven trophies in his first 500 games and none in his second half-century.

As the anniversary approached, he emphasised the importance of top-four finishes, of consistency.

We all joined the Arsène Wenger Appreciation Society to salute a manager (and a man) of real class. But the fixture list was not joining in.

Wenger ended up in the kitchen at his own party, wishing everyone would leave. Fans of Mike Leigh’s plays will appreciate the joke by one tweeter who called this “the most unsuccessful party since Abigail’s”.

The lyricism and wisdom of Wenger’s look-back at the Arsenal training ground on Friday was blown away by Mourinho’s marauding team in “10 amazing minutes,” to quote the Chelsea manager, who said “we came to kill”.

Chelsea’s power, pace and defensive strength was too much for an Arsenal side who looked frail, small, floaty and ill-equipped to win this title race, which will now be fought out by Chelsea, Liverpool and City. West London has a hex on the north. Spurs went down 4-0 here two weeks ago.

“Specialist in failure,” chanted Chelsea’s fans, reviving Mourinho’s taunt. The patience operated by (and extended to) Wenger by the Arsenal board appears to be viewed by Mourinho as some kind of personal affront.

What is it: jealousy? Contempt for Wenger’s philosophy? Either way he found a weapon far more powerful than press conference slurs.

This was the joint-highest margin of defeat endured by Wenger in his thousand games, matching the 8-2 defeat at Manchester United in August 2011.

That day Sir Alex Ferguson felt sorry for Wenger. An internal voice said “enough” when the score reached seven. The point about Arsenal’s frailty had been made.

There was no such sympathy here for Wenger, whose future is once more in doubt, at least until the FA Cup has been played out. Those Arsenal fans who feel his reign has run its course will feel emboldened to say again that the farewells should be said in May.

Plainly Arsenal are in a pattern where paradise never comes. The squad bristles with good young players. Most have been signed to long-term deals.

No Premier League club would turn away Aaron Ramsey, Theo Walcott, Oxlade-Chamberlain, Jack Wilshere, Gibbs and Serge Gnabry. But at the core of the last few years has been an inability to sustain the challenge for major honours. There is a kind of conviction deficit that shows in the biggest matches.

Wenger left Stamford Bridge without attending the usual press conference.

The press office staff said he had spoken to newspaper reporters for Monday’s editions. But this was a sad postscript to Friday’s Arsène Wenger love-in, with its celebratory, respectful tone.

It was no more than he deserved. We see now, though, how he has walked the rim of the volcano since Arsenal’s last major trophy, in 2005. The mantra of consistency, improvement and financial prudence cannot withstand the turbulence of 6-3, 5-1 and 6-0 defeats to the club’s biggest rivals.

Injuries are a factor, clearly, but are not a get-out-of-jail card. On the simplest level, Wenger’s reliance on Olivier Giroud up front is an indictment of transfer policy.

Giroud, beset by personal problems, lumbered at Spurs and lumbered again here. The concession of those two early goals, meanwhile, pointed to poor preparation, mentally and tactically.

Opinions on Arsenal have lurched this way and that all season. If they win the FA Cup the reviews may turn again.

Undeniably, though, the nature and scale of this defeat will deepen the suspicion that Wenger’s teams can go so far towards success but then no further. Year after year we see promise and potential unravel.

A reckoning is coming, on all sides. This thousandth game started out as a chance to praise a lifetime’s work. It ended with another “scar” on Wenger’s heart. A really nasty one.